In concept, environmental impact assessment (EIA) and risk assessment (RA) have evolved as parallel and sometimes overlapping procedures for rational reform of policy making. With other forms of policy analysis, such as applied systems analysis, as well as cost-benefit and cost-effectiveness analysis, they share the common presumption that policy decisions can be improved by the application of explicit analysis and documentation. Both are intended to provide reasoned predictions of the possible consequences of policy decisions and, thus, to permit wiser choices among alternative courses of action.
In practice, however, EIA and RA have been nurtured by different disciplinary and professional communities in largely separate policy contexts. As a result, they have evolved differences of emphasis, both in substance and in process, which merit notice and reflection. Some of these differences reflect the varying functions of the two types of analysis, but others suggest opportunities to improve both EIA and RA by the transfer of features from one to the other.
Many of the policy decisions most in need of analysis, in fact, require some combination of both. Generally, a systematic identification of possible environmental impacts, as well as a rigorous analysis of their magnitude and probability is required. Examples include offshore hydrocarbon developments; environmental applications of pesticides; new biotechnologies; siting of potentially hazardous industrial facilities; as well as a wide range of others. Exactly what the combination of the two approaches should be, and how the breadth of impact identification should be traded off against the depth of predictive analysis for key impacts, is an important question for study.
Both EIA and RA, therefore, could probably benefit by learning from each other and, in many cases, by consolidation into a unified process. The purpose of such a process, however, is not merely to produce the most quantitatively sophisticated estimate of particular risk, nor the most comprehensive list of possible environmental impacts. It is, rather, to produce a rationale for making public policy decisions that is both well reasoned, and recognized as legitimate and acceptable by the public.
This chapter recommends two particular topics for research. The first is to develop protocols for unified environmental impact and risk assessment of